The invention concerns the field of MANET (Mobile Ad hoc Network) routing protocol ad hoc networks, and more specifically the generating of hierarchical trees within such networks.
As experts know, point-to-multipoint (or multicast) routing protocols were initially designed for wireline networks and are therefore poorly suited (or even completely unsuited) to ad hoc networks.
To allow the use of multicast routing in ad hoc networks, several protocols were therefore proposed. These protocols use either mesh-based routing or tree-based routing.
Mesh-based multicast routing consists of defining several paths between each source router of a network and the receiving routers. This routing method is relatively well suited to the mobility of network devices as it allows the transmitting of data packets if a link between two routers is interrupted. It offers the advantage of requiring few control packet exchanges to generate and update the mesh. However, it does not optimize the use of the bandwidth within the network and does not facilitate increases in the network's load.
Tree-based multicast routing consists of defining a single optimum routing path between a source router and receiving routers. It is based on the generating and updating of trees by means of mechanisms (or processes) such as AMRIS, MAODV, LAM and LGT.
A MANET routing protocol may be reactive (in other words, the router must request a path when necessary as it doesn't know the network's topology) or proactive (each router may calculate a path when necessary as it knows the network's topology).
AMRIS (Ad hoc Multicast Routing protocol utilizing Increased ID numberS) is a process requiring a large number of control packets to generate and update trees and as such is not suited to the mobility of network devices. Indeed, significant time is required to reconstruct a tree when routers move. Furthermore, during the tree reconstruction phase the data packets are lost.
MAODV (Multicast Ad hoc On-Demand Distance Vector) is, for example, described in the article “Multicast Operation of the Ad-hoc On-Demand Distance Vector Routing Protocol” by Elizabeth M. Royer and Charles E. Perkins, published on 15 Aug. 1999, in Mobicom'99, Proceedings of the 5th annual ACM/IEEE International Conference on Mobile Computing and Networking. It is a process mainly intended to operate with the AODV protocol, which is a reactive MANET protocol. It uses the broadcasting of control packets to signal each movement of a router, which overloads the ad hoc network.